The technology explosion in the medical device industry has resulted in a variety of innovative diagnostic and therapeutic devices and methods. Many implantable medical devices (IMDs), for example, including pacemakers, cardioverter-defibrillators and neural stimulators, are operatively coupled to electrodes, which are joined to elongate lead wires that extend from the devices to a target site either on or within a body of a patient. The electrodes may deliver stimulation therapy and/or sense electrical signals from the patient, for example cardiac depolarization signals, which are used to guide or dictate therapy delivery.
Patients, in which such leads are implanted, may be exposed to a substantial amount of radio frequency (RF) energy, for example, when subject to magnetic resonance imaging (MRI) or radio diathermy processes. An implanted lead wire can act as an antenna during exposure to these RF signals and an appreciable amount of current may thereby be generated in the lead wire, resulting in high current concentration at a surface of a tissue-contacting electrode, for example, implanted to provide pacing stimulation. Much of this current produces heat, due to energy dissipated in a resistance of the electrode-to-tissue interface, which may result in tissue damage in proximity to the electrode. Leads that include an energy dissipating shunt component have been described, for example, in co-pending and commonly-assigned patent application Ser. No. 11/426,207, but there is still a need for novel lead body designs that incorporate more effective energy dissipating shunts.